Ultra-fast photothermal-responsive Fe-TCPP-based thin-film nanocomposite membranes for ON/OFF switchable nanofiltration

Metal organic frameworks (MOFs) based Nanofiltration (NF) membranes have promising advantages in the separation of dyes and salts to purify the industrial polluted water. Herein, we report the synthesis of porphyrinic, porous and ultra-fast photothermal sensitive iron tetrakis(4-carboxyphenyl)porphyrin) (Fe-TCPP) MOFs nanofibers and the corresponding thin film nanocomposite (TFN) membranes by facile interfacial polymerization (IP). The Fe-TCPP nanofibers based TFN membrane enhances the pure water permeance to 28.1 L.m(-2).h(-1).bar(-1) (i.e., 3.5-fold higher than thin film composite (TFC)) by providing continuous hydrophilic flow pathways to permeate. The Fe-TCPP nanofibers contribute to the surface of TFN membrane, resulting not only fast permeation, but also ultra-high rejection of dyes i.e., 97.2%, 98.3% and 99.1% for Indocyanine Green, Brilliant Blue-R and Direct Red-80, respectively. Additionally, the TFN membrane also demonstrates 23-43 % salts rejection. Due to the ultra-fast photothermal responsive nature of Fe-TCPP nanofibers (88.4 degrees C increased temperature in 2 sec photo exposure), the water permeation of TFN NF membrane increases 30 % with 0.5 min under visible light-irradiation. This photo-induced ON/OFF separation is switchable. The enhanced permeation, high dyes rejection and photo-modulated ON/OFF nano-separation opens a new avenue for TCPP-based MOFs in the water purification technologies.

Automated summary

MOFs-based NF membranes with Fe-TCPP nanofibers exhibit enhanced pure water permeance and high dyes rejection, as well as moderate salts rejection. The ultra-fast photothermal responsive nature of Fe-TCPP nanofibers enables photo-modulated ON/OFF nano-separation for water purification applications.